This career development award will establish Dr. Ryan Greysen, a hospitalist at the University of California, San Francisco as a clinician-investigator focused on core geriatric vulnerabilities (functional, cognitive, and social) that impact hospital outcomes among older adults. This K23 award will provide Dr. Greysen the support needed to accomplish 4 goals: (1) to become an expert patient-oriented outcomes researcher in aging research; (2) to elucidate risk factors for readmission among vulnerable older adults and understand the mechanisms by which these factors directly impact patients/caregivers; (3) to develop expertise in mixed methods research through use of advanced quantitative and qualitative techniques (4) to develop leadership in health policy at the intersection of hospital medicine and geriatrics. To achieve these goals, Dr. Greysen has assembled an expert multidisciplinary team in geriatrics, quantitative and qualitative methods, and health policy research. His primary mentor, Dr. Kenneth Covinsky, has extensive experience in aging outcomes research and mentoring junior faculty to become independent investigators in aging research. His co-mentors are Dr. Andrew Auerbach, an expert in quantitative analysis of hospital quality of care and implementation science, and Dr. Daniel Dohan, a leading expert in qualitative analysis of social determinants of health and health policy. Dr. Greysen will also benefit from the expertise of two distinguished scientific advisors with expertise in advanced biostatistics and mixed methods research. Hospital readmission is a common, costly, and important event in the health trajectory of older adults. Dr. Greysen's research plan builds on his preliminary data to examine the impact of functional, cognitive, and social vulnerabilities on readmission for Medicare patients. He will study these effects by adding data about these vulnerabilities from the nationally-representative Health and Retirement Survey (HRS) to Medicare claims data and modeling the same analytical approach used by Medicare to penalize hospitals for higher than expected rates of 30-day readmission (Aim1a-c). To maximize the immediate policy impact of this research, Dr. Greysen will also conduct a subgroup analysis of patients admitted with heart failure, heart attack, or pneumonia to mirror the initial implementation of this controversial Medicare policy in 2012 (Aim 1d). Dr. Greysen will also conduct in-depth qualitative data collection and analysis with hospitalized older adults with functional, cognitive, and social vulnerabilities recently discharged from two hospitals (one large public and one large academic hospital) in one city (Aim 2). This aim will explore mechanisms by which vulnerability directly impacts efforts of older adults and caregivers to recuperate from hospitalization and enable future interventions targeting these patients. This research plan leverages existing UCSF and NIA resources of Dr. Covinsky's geriatric outcomes research group and the HRS-Medicare dataset. Finally, this research will form the basis for an R01 application to study interventions to improve outcomes of transition care for hospitalized older adults.